title: Growth phase dependent stop codon readthrough and shift of translation reading frame in Escherichia coli.
abstract: Nonsense codon readthrough and changed translational reading frame were measured in different growth phases in E. coli. The strains used carry plasmid constructs with a translation assay reporter gene. This reporter gene contains an internal stop codon or a run of U-residues. Termination or frameshifting give rise to stable proteins that can be physically quantified on gels along with the complete protein products. Readthrough of the stop codon UGA by a nearcognate tRNA is several fold higher in active growth than in late exponential phase. In early exponential phase, about 7% of -1 frameshift at a U9 slippery sequence is detectable; upon entry to stationary phase this frameshifting increases to about 40% followed by a decrease in stationary phase. A similar increase is observed in the case of +1 reading frameshift at the U9 sequence, which increases from 13% in early exponential growth phase up to 38% at the beginning of stationary phase followed by a decrease. Thus, the levels of both stop codon readthrough and frameshifting are growth phase dependent, though not in an identical fashion.
authors.affiliation: Department of Microbiology, Stockholm University, Sweden.
authors.forename: A M
authors.initials: AM
authors.lastname: Wenthzel
authors.forename: M
authors.initials: M
authors.lastname: Stancek
authors.forename: L A
authors.initials: LA
authors.lastname: Isaksson
mesh_terms: D001483:Base Sequence; D018388:Codon, Terminator; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D018965:Frameshifting, Ribosomal; D008969:Molecular Sequence Data; D016364:Reading Frames
chemical_list: D018388:Codon, Terminator; D004269:DNA, Bacterial